Starting circuit for electrical discharge devices



March 20, 1956 c. M. RIVELY ET AL 2,739,268

STARTING CIRCUIT FOR ELECTRICAL DISCHARGE DEVICES Filed March 11, 1953 Fig. I.

WITNESSES: INVENTORS Clair M. Rively ond 9,41 5 A-; RoBgeri E. Peterson ATTORNEY United States Patent O i STARTING CIRCUIT FOR ELECTRICAL DISCHARGE DEVICES Clair M. Rively, Rockaway, and Robert E. Peterson, Cedar Grove, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 11, 1953, Serial No. 341,734

8 Claims. (Cl. 315-490) Our invention relates generally to a starting device for electrical discharge devices, and more particularly to a starting device for short are mercury vapor lamps, which provides for most efficient operation when supplied from an alternating current source.

In starting electrical discharge devices such as mercury vapor lamps, the voltage necessary to start or restart the discharge greatly exceeds the open circuit voltage of the supply line, which is, however, sufficient to maintain the discharge. Heretofore, various starting devices have been manufactured to obtain high starting voltages which have not been entirely satisfactory due to various factors, such as a high initial cost, short sewice life, limited range of operation or too high maintenance cost, or excessive bulk.

We provide a simple starting device which has few auxiliary components for obtaining the necessary high starting voltage. Our device is also applicable to start discharge devices wherein the starting voltage is only slightly higher than the open circuit voltage of-the supply line.

Accordingly, one object of our invention, generally stated,is to provide an improved starting device for electrical discharge devices.

A more specific object of our invention is to provide a starting device for electrical discharge devices requiring few auxiliary members to obtain the necessary high starting voltage.

. Another object of our invention is to provide an inex pensive starting device for electrical discharge devices both in initial cost and servicing.

Another object of our invention is to provide a starting device for electrical discharge devices which does not require any of the component parts to be calibrated.

Still another object of our invention is to provide a starting device for electrical discharge devices having simplified and economical component parts.

A further object of our invention is to provide a starting device for electrical discharge devices which may be utilized throughout a large range of starting voltages.

Still another object of our invention is to provide a starting device for high pressure discharge devices which produces rapid flux changes in a starting transformer to obtain the high necessary starting voltage.

These and other objects of our invention will become more apparent upon consideration of the following detailed description of a preferred embodiment thereof, when taken in conjunction with the attached drawing, wherein:

Figure l is a schematic circuit diagram of a starting device embodying the features of our invention.

Figure 2 is an enlarged view of the central portion of the starting device shown in Fig. 1 showing the vibrating memberat a different position in bridging relationship with the center legs of the starting device.

Referring to Fig. l, the circuit shown as a preferred 2,739,268 Patented Mar. 20, 1956 ice and requires a starting voltage to be impressed across the electrodes 4 and 6 which is considerably higher than the voltage of the supply circuit. For example, a discharge device which is designed for normal operation with a voltage of volts may require voltages of 300 to 1,000 volts to be impressed across the electrodes before any discharge will occur. In order to obtain such initial high starting voltages the discharge device is supplied from a source 8 of alternating current which, by means of switch 10, is connectible to the primary 12 of transformer 14. Transformer 14 comprises a unitary three-legged core structure having spaced apart cross yokes 15, outside legs 16 and 20 which are integral with yokes 15, and a center leg 21. The center leg 21 consists of a lower core member 22 which may be formed integral with the lower yoke 15 and an upper core member 24 which may be formed integral with the upper yoke 15, and is separated from the lower core member 22 by an air gap 26. If desired a suitable insulating material may be placed in air gap 26 in order to obtain increased rigidity of transformer 14, as long as the requisite magnetic gap 26 is maintained in the center leg 21 of the transformer 14.

The primary winding 12 is wound on one of the outside legs of transformer 14, and a secondary winding 18 is wound on the other outside leg of transformer 14. As shown the primary winding 12 is wound around leg 16 and the secondary Winding 18 is wound around leg 20. The ends of the secondary winding 13 are connected by conductors 23 and 25 to electrodes 4 and 6, respectively, of discharge device 2 to provide a secondary circuit.

Due to the air gap 26 in the center leg 21 of the transformer 14 the reluctance of the center leg 21 is higher than the reluctance of outside leg 20. Consequently, the

flux produced across air gap 26 is smaller in value than the flux produced in leg 20 of transformer 14. However, by increasing the magnetomotive force across leg 20 due to the current fiow through the secondary 18 the flux density across the air gap 26 may be increased. It is the purpose of our invention to vary the magnetic flux across the air gap 26 to obtain the high starting voltage required by discharge device 2. This purpose is accomplished by attaching a spring 28 of any suitable resilient material, such as a Phosphor-bronze alloy, to upper core member 24 of the center leg 21 of transformer 14, by any suitable means such as brazing or welding.

As more clearly shown in Fig. 2, a bar member 30 formed from any suitable magnetic material such as soft iron is attached to the free end of spring member 28 by any suitable means, such as by brazing, and is supported by spring member 28 in the magnetic field produced across air gap 26. In order that bar member 30 may also function as a contact member, a contact 33, formed from any suitable are resistant, and good electrical conducting material, such as a tungsten and silver alloy, is positioned on the side of bar member 30 opposite the gap 26, and is attached thereto by any suitable means, such as brazing. As more clearly shown in Fig. 2, bar member 30 is physically proportioned so that when attracted towards the center leg 21 of transformer 14, the air gap 26 is magnetically bridged thereby. A fixed contact 32 is positioned to be engaged by the movable contact 33 when the spring member 28 and bar member 30 are in their normal unrestrained position, that is, when released from the magnetic field produced across the air gap 26 of the transformer 14. Fixed contact member 32 is directly connected to one end of the secondary coil 18 by a conductor 27, while the other end of the secondary 18 is connected by a conductor 29 to resistance 36, which in turn is connected to the bar member 30 by a conductor 31 and flexible conductor 34. The flexible conductor 34 is utilized between conductor 31 and bar member 30 in 7 order that bar member 30 will be electrically connected to the secondary 13 of transformer 14 regardless of the position'of bar member 30. Thus a second circuit is provided across the secondary 13 of the transformer 14 in parallel to the previously described circuit to the electrical discharge device 2. V A

In the operation of this embodiment of the invention, when the switch It? is closed, a current will How in the primary 12 of the transformer 14 and induce a Voltage in the secondary 18 of transformer 14 which will cause a current to flow through the closed circuit comprising conductor 2%, resistance 36, conductor 31, flexible conductor 34, bar member 39, movable contact 33, fixed contact 32 and conductor 27. The magnitude of such current flow. is dependent upon the physical characteristics of the resistance 36 which may be varied to obtain a particular magnitude of current flow. For the purposes of this invention, the value of resistance 36 is such as to produce a flux across air gap 26 in the center leg 21 of the transformer 14, sufficient to attract the bar member 30 toward the air gap 26. The attraction of bar member 30 is achieved as the current flow in resistance 36 creates a back magnetomotive force across the secondary 18 of the transformer 14 which opposes the magnetornotive force across the primary 12 of the transformer 14 which tends to oppose the building up of the current in the secondary circuit by the primary and decreases the flux density in the leg 29 of the transformer 14. Consequently, a greater flux density is produced in the center leg 21 of the transformer 14 which causes a substantial flux field to be created across the air gap 26, which in turn causes the bar member St; to be attracted to' and move inward, while flexing the spring 28, against the upper and lower core members 2% and 22 of the center leg 21 of transformer 14, thereby magnetically bridging the air ap 2&5. With the sprihg 28 and bar member 30 in this position, there is no current flow across the secondary 13 of the transformer 14, as both parallel secondary circuits, that is, through the discharge device 2 and the resistance 36, respectively,

are open. The discharge device 2 is in itself an open circuit 'until such time as an arc may be struck across the electrodes 4 and 6 and the resistance load 36 is open when bar member moves inward towards the air gap 26 in the center leg 21 of the transformer 14 and disengages the fixed contact 32 (Fig. 2) Consequently, the current flow in the secondary 18 of transformer 14 end denly drops to zero, thereby causing a rapid change in the flux field around the secondary 18. Primary 12 of the transformer 14 at all times attempts to sustain the current flow and the flux field through the secondary 18 of transformer 14. Due to the characteristics of the Y circuit the flux field created by the primary 12 and the rapid change in the field of the secondary 18 are additive, and a high open circuit voltage is impressed across the discharge device 2 which may be sufficient to break down and start the electrical discharge device 2.

In the event that the electrical discharge device 2 does not start after once having a high open circuit voltage impressed across the electrodes 4 and 5, the spring 28 and bar 3t} due to the normal spring action of spring 28 return to their normal position where contact 33 is in engagement with fixed contact member 32, as there is nocurrent flow in the secondary circuit toproduce a fiux field across air gap 26 of the center leg 21 of the transformer '14 to bias spring 28 inward. 23 and bar member 3% return to their initial position, the resistance load 36 is again placed across the secondary 18 of transformer 14 and a resultant current is induced in the secondary 18 of transformer 14 As previously described, bar member 30 is again attracted to the center leg 21 of transformer 14, and again a high open circuit voltage is impressed across the electrical discharge device 2. a

By proper selection of the electrical and mechanical elements, such vibratory action will continue until the electrical discharge device 2 sustains a current flow,

When spring member thereafter transformer 14 produces a sufficient voltage across the secondary 13 to maintain the discharge across the discharge device 2. Once the discharge device 2 is operating the secondary 18 of the transformer 14 produces a back magnetomotive force due to the current flow across the discharge device 2 in a similar manner as when there was a current fiow through the resistance 35 as previously described. Also in this same manner such bacit magnetomotive force decreases the flux density in which results in an increased flux density across the p of the center leg 21 of the transformer 14. the flux field across the air gap 26 is thereby maintained and bar member 3% remains bridged across air gap 26 and remains in such position as long as the discharge device 2 is operative. If for any reason the discharge dev'cc 2 were to fail or if the switch 1% opened, the llux across air gap 26 would collapse thereby releasing member 3%) from engagement with upper core memher 22. and lower core member 24 across air gap 26, and

member 34 would be returned to its normal unrestrained position by spring 23. Under these conditions spring 28 would return bar member 3% in engagement with contact 32 so that it would be possible to restart the same or another discharge device which may be inserted across the secondary iii of transformer 14.

From the foregoing description of the device utilizing the principles of our invention it is obvious that the auxiliary components required are inexpensive and extremely durable. Also these components require iittle space so that the entire starting device can be fabricated as a unit and adjusted to obtain-optimum operating conditions durir brication. Thus existing installations of discharge devices may be converted to utilize the starting device incorporating the featuresof our invention without difiiculty. Another advantage obtained byv using such a unit is that once installed no maintenance is required with regard to the adjusting of the starting device thus eliminating any further expense withregard to the starting device. 7

Although we have shown and described one specific embodiment of our invention, we are aware that other modifications thereof are possible within the broad spirit and scope of this invention. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and the spirit of the invention.

We claim as our invention:

1. A starting device for an electrical discharge device comprising, a transformer core defining a closed magnetic circuit, a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, means for impressing a high voltage across said electrical discharge device comprising a normally closed first circuit connected across said secondary coil independent of the electrical discharge device for causing a current flow in said secondary coil, a movable means responsive to said current flow in said secondary coil to open said first circuit whereby a high voltage surge is produced across said electrical discharge device, and means for rapidly. reestablishing said first circuit if said surge is insufficient to produce a current flow in the electrical discharge device.

2. A starting device for an electrical discharge device comprising, a transformer core defining a closed magnetic circuit, a primary coil and a secondary coil each positioned on said core, said core also having a portion the reluctance of which varies in response to current flow in said secondary, said secondary ,coil being adapted to be connected to an electrical discharge device, means for impressing a high voltage across said electrical discharge device, said means comprising a normally closed first circuit connected across said secondary coil independent of the electrical discharge device for causing a current flow in said secondary core, said first circuit including a pair of separable contacts which are separable upon movement of, a magnetic means located in proximity to said masses portion of said core, said magnetic means being movable in response to the variation in reluctance in said portion of said core due to said current flow in the secondary coil to separate said contacts so that said current flow in said secondary coil is discontinued and a high voltage surge is produced across said discharge device, resilient means for normally supporting said magnetic means so that said contacts are closed, and said resilient means being stressed by such movement of said magnetic means so that said magnetic means is returned to said normal position when there is no current flow in said secondary.

3. A starting device for an electrical discharge device comprising, a transformer core defining a closed magnetic circuit, a primary coil and a secondary coil each positioned on said core, said core also having a portion the reluctance of which varies in response to current fiow in said secondary, said secondary coil being adapted to be connected to an electrical discharge device, means for impressing a high voltage across said electrical discharge device, said means comprising a normally closed first circuit connected across said secondary independent of said electrical discharge device for causing the reluctance of said portion of said core to vary a first time, a movable means responsive to said first variation in reluctance to open said first circuit whereby a high voltage surge is produced across said electrical discharge device, and the reluctance of said portion is varied a second time, and means operative in response to said second variation to move said movable means to reestablish said first circuit.

4. A starting device for an electrical discharge device comprising, a transformer core defining a closed magnetic circuit, a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, a first circuit connected across said secondary coil, said core having a portion the reluctance of which varies depending upon whether current flows in said secondary coil, said first circuit including normally closed contact means whereby a current will flow in said secondary coil when said primary is energized, a movable means responsive to the flux created in said portion of said core by said current flow in said secondary coil, to open said contacts and deenergize said first circuit whereby a high voltage surge is produced across said electrical discharge device, and resilient means biasing said movable means for causing said movable means to return and reestablish said first circuit if said surge is insufficient to cause a current flow across said electrical discharge device.

5. A starting device for an electrical discharge device comprising a transformer core defining a closed magnetic circuit having a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, a first circuit connected across said secondary coil, said core having a bridge the reluctance of which varies depending upon whether current flows in said secondary coil, said first circuit including normally closed contact means whereby a current will flow in said secondary coil when said primary is energized, a magnetic means located in proximity to said bridge responsive to the flux created in said bridge by said current flow in said secondary core, to open said contacts and deenergize said first circuit whereby a high voltage surge is produced across said electrical discharge device, and resilient means engageable with said movable means for causing said movable means to reestablish said first circuit if said surge is insufiicient to cause a current flow across said electrical discharge device.

6. A starting device for an electrical discharge device comprising a transformer core defining a closed magnetic circuit having a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, a first circuit connected across said secondary independent of said electrical discharge device for causing a current to flow in said secondary coil, said core having a bridge in which the flux varies depending upon whether current flows in said secondary coil, said first circuit including contact means one of which is supported by a magnetic means located at a first position in proximity to said bridge, supporting means for said magnetic means so that said contact means are normally closed, said magnetic means being responsive to said flux variations in said bridge due to said current flow in said secondary coil whereby said magnetic means is moved toward said bridge to a second position where said contacts are opened and a high voltage surge is produced across said electrical discharge device, and said supporting means being resilient to rapidly return said magnetic means to said first position ifsaid surge is insufiicent to cause a current flow across said electrical discharge device.

7. A starting device for an electrical discharge device comprising a transformer core defining a closed magnetic circuit having a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, a first circuit connected across said secondary independent of said electrical discharge device for causing a current to flow in said secondary coil, said core having a bridge portion in which the flux varies depending upon whether current fiows in said secondary coil, said first circuit including contact means one of which is supported by a magnetic means located at a first position in proximity to said bridge, supporting means for said magnetic means so that said contact means are normally closed, said mag netic means being responsive to said tlux variations in said bridge due to said current flow in said secondary coil whereby said magnetic means is moved so that said contacts are opened and a high voltage surge is produced across said electrical discharge device, said first circuit having a characteristic so that sufficient flux is created in said bridge to cause said magnetic means to be moved into bridging relationship with said bridge, and said supporting means being resilient to rapidly return said magnetic means to said first position if said surge is insutficient to cause a current flow across said electrical discharge device.

8. A starting device for an electrical discharge device comprising a transformer core defining a closed magnetic circuit having a primary coil and a secondary coil each positioned on said core, said secondary coil being adapted to be connected to an electrical discharge device, and means for rapidly impressing a series of high voltage surges across said electrical discharge device, said means comprisinga first circuit connected across said secondary coil having a pair of separable contact members one of which is secured to a magnetic spring biased member having a normal position so that said first circuit is closed when said primary is initially energized whereby a current Flows in said secondary coil, said magnetic member being located in proximity to a portion of said core in which the fiux increases when a current flows in said secondary coil so that said magnetic member is moved into engagement with said core portion causing said contacts to separate, said separation of said contacts causing said first circuit to be deenergized to cause a high voltage surge across said discharge device, and said spring being stressed upon movement of said magnetic member into engagement with said core portion so that said magnetic member is rapidly returned to said normal position if said surge is-insufiicient to cause a current flow across said electrical discharge device.

References Cited in the file of this patent UNITED STATES PATENTS 2,170,456 Lord Aug. 22, 1939 2,310,149 McDermott Feb. 2, 1943 2,523,020 Hehenkamp et a1 Sept. 19, 1950 

